The national airline of the United Arab Emirates, which operates from its hub in Abu Dhabi, said it had now reached the stake level approved by the Australia's Foreign Investment Review Board.
Chief executive James Hogan said in a statement the increased stake reflects Etihad's commitment to the Australian market and to the 10-year strategic partnership it concluded with Virgin Australia in 2010.
"The strategic partnership continues to deliver significant revenue streams and other benefits to each airline," said Hogan.
Air New Zealand and Singapore Airlines also hold large stakes in Virgin Australia.
Etihad's development strategy has rested on taking minority stakes in selected airlines and concluding partnerships.
It holds stakes in airberlin, Air Seychelles and Aer Lingus. It is to take 49 percent in Air Serbia in January and is waiting for approval of a 24 percent stake in Jet Airways in India.